JP6094910B2 - Method for manufacturing cylindrical battery - Google Patents

Description

  The present invention relates to a method for manufacturing a cylindrical battery, and more particularly to a method for manufacturing a cylindrical battery that facilitates increasing the capacity of the battery.

  In recent years, as electronic devices are rapidly becoming cordless, there is a growing demand for secondary batteries that are small, lightweight, and have high energy density as these power supplies. Conventionally, in such a battery, an electrode group formed by winding a positive electrode and a negative electrode in a spiral shape with a separator interposed therebetween is housed in a metal battery can (battery case). After a predetermined amount of electrolyte is injected into the case, the upper part of the battery case is sealed with a sealing plate that also serves as either a positive electrode or a negative electrode.

  On the other hand, in order to facilitate the insertion of the electrode group into the battery can and improve the productivity, the outer diameter of the electrode group is made somewhat smaller than the inner diameter of the battery can and a gap is created between them. . In this case, if the gap is left as it is, the wound electrode group is loosened and the battery performance may be lowered. For this reason, the diameter of the battery can is reduced after the electrode group is inserted into the battery can (see Patent Documents 1 and 2).

Japanese Patent Laid-Open No. 57-130368 JP 7-314056 A

  In Patent Document 1, the battery can is reduced to a desired outer diameter by inserting the battery can from the lower side (bottom side) into a cylindrical die whose inner diameter is smaller than the initial outer diameter of the battery can. . For this reason, when the lower part of the side wall of the battery can comes into contact with the die and the diameter reduction of the battery can is started, the battery can is formed such that the bottom outer surface swells outward due to distortion when the battery can is reduced in diameter. It may be deformed. As a result, the battery shape cannot be formed into a desired shape, and it is difficult to manage the battery height to the desired height.

  Patent Document 2 uses a ring-shaped die to reduce the diameter of the battery can in the same manner as Patent Document 1, and presses the receiving die from the lower side to the bottom of the battery can to reduce the diameter. Is trying to prevent undesirable deformation of battery cans.

  In Patent Document 2, since the receiving die is pressed against the peripheral edge of the bottom of the battery can (see FIG. 2 of Patent Document 2), it is possible to prevent the portion from bulging outward (lower side). However, when the deformation force acting on the bottom of the battery can at the time of diameter reduction is large, it is not possible to prevent the center of the bottom from bulging outward.

  For the above problem, it is also conceivable to suppress the center portion of the bottom portion from bulging outward by pressing the receiving die against the entire bottom portion from below. However, when the receiving die is pressed against the entire bottom portion from the lower side, the reduced diameter distortion may not act in the direction in which the bottom portion swells outward, but may act in the direction in which the bottom portion is recessed inward. As a result, as in the case where the bottom portion swells outward, a defective appearance of the battery occurs, and problems such as a defective contact when the battery is mounted on a predetermined device occur.

  Further, it is conceivable to correct the deformation generated in the bottom portion later. However, once the generated deformation is corrected later, it is difficult to obtain a highly accurate plane.

The present invention is a method for producing a cylindrical battery comprising an electrode group including a positive electrode, a negative electrode and a separator, and a battery can containing the electrode group,
The battery can includes a circular bottom, a cylindrical side wall having an open end, and a connection between the bottom and the side wall,
A step (a) of reducing the outer diameter Dc of the side wall from the initial outer diameter D1 after inserting the electrode group into the battery can;
The step (a) includes the step (a1) of inserting the battery can from the bottom side into a ring-shaped die having an inner diameter Dd smaller than the initial outer diameter D1, and the die at the opening end. Including a step (a2) of applying a diameter-reducing force to the battery can by relatively moving in the direction of
When the die and the battery can come into contact with each other and the application of the diameter reducing force is started, the contact start portion of the battery can is more than the inner surface of the peripheral edge of the bottom portion in the connection portion. position near the axial direction of the opening end portion side of the is,
Wherein the connecting portion of the battery can be subjected to step (a), that has only one bent portion having the battery the outside surface of the can battery can curvature radius R2 along the axial direction of the cylinder The present invention relates to a method for manufacturing a type battery.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the cylindrical battery which can suppress the deformation | transformation of the bottom part when shrinking a battery can easily and effectively can be provided.

  The novel features of the invention are set forth in the appended claims, and the invention will be further described by reference to the following detailed description in conjunction with the other objects and features of the invention, both in terms of construction and content. It will be well understood.

It is a partial cross section figure which shows an example of the battery manufactured by the manufacturing method of the cylindrical battery which concerns on one Embodiment of this invention. It is sectional drawing of the battery can used for the battery of FIG. 1A. It is a front view which shows schematic structure of an example of the diameter reducing apparatus which diameter-reduces the cylindrical battery of FIG. It is a front view which shows schematic structure of the other example of the diameter reducing apparatus which diameter-reduces the cylindrical battery of FIG. It is sectional drawing of a battery can and a die | dye which shows the positional relationship of the bottom part of a battery can and a dice | dies for diameter reduction when reducing the diameter of a cylindrical battery with the manufacturing method which concerns on one Embodiment of this invention. It is sectional drawing which took out and showed only the connection part of the bottom part and side wall of a battery can from FIG. 3A. It is sectional drawing which cut | disconnected the die | dye by the plane containing a central axis. It is sectional drawing of a battery can and a die | dye which shows the positional relationship of the bottom part of a battery can when reducing the diameter of the cylindrical battery of the comparative example 1, and the dice | dies for diameter reduction. It is sectional drawing of a battery can and a die | dye which shows the positional relationship of the bottom part of a battery can when reducing the diameter of the cylindrical battery of the comparative example 2, and the dice | dies for diameter reduction. It is sectional drawing of a battery can and die | dye which shows the positional relationship of the bottom part of a battery can when reducing the diameter of the cylindrical battery of the comparative example 3, and the dice | dies for diameter reduction.

  The present invention relates to a method of manufacturing a battery including an electrode group including a positive electrode, a negative electrode, and a separator, and a battery can that accommodates the electrode group. Here, the battery can includes a circular bottom portion, a cylindrical side wall having an open end, and a connection portion between the bottom portion and the side wall. The connecting portion is configured from a position at the beginning of bending at the boundary with the bottom of the battery can to a position at the end of bending at the boundary with the side wall. And the manufacturing method of this invention is equipped with the process (a) of reducing the outer diameter Dc of a side wall from the initial outer diameter D1 to the desired outer diameter D2, for example, after inserting an electrode group in a battery can.

  The step (a) includes the step (a1) of inserting the battery can from the bottom side into a ring-shaped die having an inner diameter Dd smaller than the initial outer diameter D1, and the die at the open end of the side wall of the battery can A step (a2) of applying a diameter-reducing force to the battery can by moving it relatively in the direction of the part.

  As shown in FIG. 3A, the contact start portion P1 when the die and the battery can come into contact with each other and the application of the diameter reducing force is started is the peripheral portion (19) at the bottom of the connecting portion (22). It is in the position of the opening edge part side of the axial direction of a battery can rather than inner side surface SA1. According to the present invention, since the contact start portion P1 is in such a position, the component force F2 in the radial direction of the battery can of the diameter reducing force F1 for reducing the diameter of the side wall of the battery can causes the battery can The side wall can be effectively reduced in diameter and can be prevented from being deformed so that the bottom is bent. As a result, it is possible to prevent the bottom portion from bulging outward (downward) or recessed inward. Furthermore, since the axial component force F3 of the battery can of the reduced diameter force F1 can be easily reduced, the side wall of the battery can can be prevented from rotating so as to fall inward, and the rotational force It is possible to prevent the bottom portion from expanding outward. At this time, when the radius of curvature of the connecting portion is R2 (see FIG. 3B) and the thickness of the peripheral edge portion of the bottom portion is t1, the radius of curvature R2 is preferably twice or more the thickness t1.

  The above points will be described in more detail. As shown in FIG. 3A, when the contact start portion P1 is above the inner side surface SA1, the component force F2 in the radial direction of the battery can of the diameter reducing force F1 due to the die is reduced from the starting point of the diameter reduction. It does not overlap with the bottom of the battery but acts to effectively reduce the diameter of the side wall of the battery can. Thereby, it is suppressed that component force F2 presses the bottom part which is circular from the outer peripheral side. Therefore, it can prevent that a bottom part bends and deform | transforms so that it may swell to the outer side of a battery can, or may be dented inside.

  Further, since it becomes easy to increase the angle θ1 between the component force F3 parallel to the axial direction of the battery can of the diameter reducing force F1 and F1, the component force F3 is made smaller than the component force F2. Becomes easy. As a result, the rotational force for rotating the side wall in the direction in which the side wall of the battery can falls inward (counterclockwise direction in FIG. 3A) can be reduced. Thereby, it can prevent that the bottom part of a battery can deform | transforms outward by the rotational force.

  In addition, the method of preventing the bottom from expanding by holding the bottom from the lower side with a receiving mold is the thickness of the can wall, the hardness of the can wall material, and the frictional force between the die and the can surface. Susceptible to factors. If these factors fluctuate, the force for expanding the bottom portion when the diameter is reduced can be increased. And when such a deformation force becomes larger than expected, it may not be possible to suppress the bottom portion from swelling only by pressing with a receiving die, or the bottom portion may be deformed so as to be recessed inside instead of swelling outward.

  Since the contact start portion P1 is above the inner side surface SA1, the diameter reducing force F1 itself becomes larger than expected, and even if the component force F2 in the radial direction of the battery can increases accordingly, the component force F2 Acts in a position that does not overlap the bottom of the battery can. For this reason, it is possible to effectively and stably reduce the diameter of the side wall of the battery can while suppressing the swelling of the bottom, regardless of the other factors described above. As a result, a cylindrical battery having a good appearance can be stably manufactured.

  Here, the diameter of the battery can can be reduced stepwise by using a plurality of dies having different inner diameters Dd and gradually inserting the battery can into the dies having a smaller inner diameter Dd. it can. Thereby, the diameter reducing force applied to the battery can by one die can be reduced. Therefore, it is possible to more effectively prevent the bottom portion from being deformed, and it is possible to manufacture a cylindrical battery having a good external shape without deformation of the bottom portion of the can.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1A is a perspective view showing an example of a cylindrical battery to which a method for manufacturing a cylindrical battery according to an embodiment of the present invention is applied. FIG. 1B shows a simplified structure of the structure of the battery can. In FIG. 1A, in order to facilitate understanding of the internal structure of the battery, a part of the battery is shown in a sectional view. In FIG. 1B, the battery can shows a state before grooving. Moreover, the broken line in FIG. 1B has shown the boundary X of a bottom part and a connection part, and the boundary Y of a side wall and a connection part.

  The battery 100 in the illustrated example is a conceptual diagram, for example, an AA nickel metal hydride storage battery, and has a circular bottom 18, a cylindrical side wall 20 having an open end 20 a, and a connection part that connects the bottom 18 and the side wall 20. A battery can 1 including 22 is provided. The battery can 1 is made of a conductive material (for example, a cold rolled steel plate such as SPCC and SPCD, or a metal such as a nickel plated steel plate). A substantially cylindrical electrode group 11 including a positive electrode 12, a negative electrode 13, and a separator 14 is accommodated inside the battery can 1 together with an alkaline electrolyte (not shown). The electrode group 11 is formed by winding a positive electrode 12 and a negative electrode 13 in a spiral shape with a separator 14 interposed therebetween. A negative electrode 13 is disposed on the outermost periphery of the electrode group 11, and the negative electrode 13 is in direct contact with the inner peripheral wall of the battery can 1.

  With the above configuration, the battery can 1 functions as a negative electrode external terminal of the battery 100. A gasket 2 formed of a ring-shaped insulating material (for example, resin) is disposed inside the opening end of the battery can 1. The open end of the battery can 1 is closed by a cover plate (sealing plate) 3 made of a conductive material (for example, metal). The sealing plate 3 is electrically insulated from the battery can 1 by the gasket 2. On the sealing plate 3, a positive terminal plate 10 having a protrusion 10a is arranged. The positive terminal plate 10 is electrically connected to the sealing plate 3.

  In the vicinity of the opening end portion of the side wall of the battery can 1, a groove portion 4 is provided along the opening end portion in order to securely fix the gasket 2. The groove 4 is formed by denting the side wall of the battery can 1 inward. The sealing plate 3 is sandwiched from above and below by the gasket 2, and the gasket 2 bends the side wall (groove forming wall) of the battery can 1 forming the groove 4 and the opening end of the battery can 1 inward. The battery can 1 is fixed to the opening end of the battery can 1 by being sandwiched between the curled portions 1a. The groove 4 in the illustrated example is compressed in the axial direction of the battery can 1.

  The sealing plate 3 has a gas vent hole 8 at the center. A rubber cylindrical valve body 9 is arranged so as to close the gas vent hole 8 from the outer surface side of the sealing plate 3. The valve body 9 is accommodated in a protrusion formed on the positive electrode terminal plate 10 and is pressed toward the sealing plate 3 with a predetermined pressure by the inner surface of the top of the protrusion. As a result, the gas vent hole 8 is normally airtightly closed by the valve body 9. On the other hand, when gas is generated in the battery can 1 and its internal pressure increases, the valve body 9 is compressed by the gas pressure, the gas vent hole 8 is opened, and the gas is released from the inside of the battery can 1. Thus, the sealing plate 3, the valve body 9, and the positive electrode terminal plate 10 form a safety valve.

  An insulating member 16 with a circular slit is disposed between one end of the electrode group 11 (end on the side of the sealing plate 3) and the sealing plate 3, and the positive electrode lead 15 connected to the positive electrode 12 passes through the slit. The positive electrode 12 and the sealing plate 3 are connected. Thereby, the positive electrode terminal plate 10 and the positive electrode 12 are electrically connected. A circular insulating member 17 is also disposed between the other end of the electrode group 11 (the end on the bottom side of the battery can 1) and the bottom of the battery can 1. And the outer surface of the battery can 1 is coat | covered with the insulating exterior label 6 except the bottom part. Furthermore, a donut-shaped insulating plate (leak prevention plate) 7 may be disposed between the curled portion 1 a and the exterior label 6.

  Next, the diameter reduction of a battery can is demonstrated. FIG. 2A shows an example of a diameter reducing device. FIG. 2B shows another example of the diameter reducing device. A diameter reducing device 30A shown in FIG. 2A includes a moving mechanism 31 that moves the battery 100 along the axial direction of the battery can 1, and a ring-shaped diameter reducing die into which the battery moved by the moving mechanism 31 is inserted. 32A.

  The moving mechanism 31 is connected to, for example, a vertical member 31a and a frame 31c having two horizontal members 31b disposed opposite to each other, an air cylinder 33 fixed to the frame 31c, and the air cylinder 33. It has a lower support member 34 that contacts the bottom of the battery and supports the battery from the lower side (bottom side) with a constant support force, and an upper support member 36 fixed to the frame 31c. The battery 100 is supported by being sandwiched between a lower support member 34 and an upper support member 36. A portion of the lower support member 34 that comes into contact with the bottom of the battery (hereinafter referred to as a receiving mold) is cylindrical, and can be brought into contact only with the peripheral edge of the bottom before the diameter reduction. Alternatively, the receiving mold can be formed so as to come into contact with the entire bottom before diameter reduction.

  The moving mechanism 31 includes an electric motor 35 that generates a driving force for moving the battery supported by the frame 31c via the lower support member 34 and the upper support member 36 downward, and its output. For example, a ball screw 37 connected to a shaft (not shown) is included. The rotational driving force generated by the electric motor 35 is converted into a linear downward driving force by the ball screw 37. The frame 31c that supports the battery is moved downward by the downward driving force, and the battery is inserted into the die 32A from the bottom side, and moves downward in the die 32A. Here, if the initial value (initial outer diameter) of the outer diameter (diameter) Dc of the battery can 1 (side wall 20) is D1, and the inner diameter (minimum diameter) of the die 32A is Dda, Dda <D1. Thereby, the diameter Dc is reduced. When the desired outer diameter after reducing the diameter of the battery can 1 is D2, D2 = Dda.

  The diameter reducing device 30B shown in FIG. 2B is different from the diameter reducing device 30A in FIG. 2A in that it includes two ring-shaped diameter reducing dies 32B and 32C. The moving mechanism 31 of the diameter reducing device 30B is the same as that of the diameter reducing device 30A. The dice 32B and 32C are arranged coaxially in the moving direction of the battery so that the battery 100 is first inserted into the dice 32B and then inserted into the dice 32C. The dies having the same shape as the dies 32A can be used for the dies 32B and 32C, except that the inner diameter can be different.

  When the inner diameter of the die 32B is Ddb (Ddb <D1) and the inner diameter of the die 32C is Ddc (Ddc <D1), Ddc <Ddb. Further, Ddc = Dda = D2. By sequentially inserting the battery 100 into the two dies 32B and 32C, the battery can 1 is reduced in diameter in stages. Thereby, the diameter reducing force applied to the battery can by one die can be reduced. Therefore, the deformation | transformation which the bottom part of a battery can bulges outside can be suppressed more effectively.

  FIG. 3A is a cross-sectional view of a portion in the vicinity of the connection portion of the battery can cut along a plane including the central axis of the battery can. FIG. 3B shows the connection portion in a cross-sectional view. FIG. 3C is a cross-sectional view showing the die cut along a plane including the central axis.

  As shown in FIG. 3C, the die 32 has a contact portion 38 that contacts the battery can 1 on the inner peripheral surface. The contact portion 38 contacts the connection portion 22 of the battery can 1 so that the diameter reduction of the battery can 1 is started. A portion (contact start portion) P1 of the outer surface of the battery can 1 when the diameter reducing force F1 starts to act on the battery can 1 due to contact with the contact portion 38 is in the axial direction of the battery can 1. It is above the inner side surface SA1 of the peripheral edge 19 (opening end side). The angle θ1 between the diameter reducing force F1 and the axially upward component force F3 of the battery can 1 is preferably 50 ° or more, and more preferably 60 ° or more. Thus, the component force F2 in the radial direction of the battery can 1 of the diameter reducing force F1 can be increased while the component force F3 in the axial direction can be decreased.

  The contact portion 38 has a cross-sectional shape such that the central portion in the axial direction protrudes in an arc shape toward the inside of the die 32. Let the radius of curvature of the cross-sectional shape of the top 38a be R1. In addition, an angle formed by the inclined portion 38b that connects the base portion 39 of the die 32 and the top portion 38a of the contact portion 38 and the axial direction of the die 32 is defined as θ2. The curvature radius R <b> 1 is preferably 1 to 5 times the thickness t <b> 1 of the peripheral edge 19 of the bottom 18 of the battery can 1. The angle θ2 is preferably 3 to 15 °.

  On the other hand, the connection part 22 of the battery can 1 also has a cross-sectional shape having an arcuate outline, and its curvature radius is R2. More specifically, in the cross-sectional view in which the battery can 1 is cut along a plane including the central axis of the battery can 1, the curvature radius R <b> 2 is the curvature radius of the outer contour line of the battery can 1 at the connection portion 22. The radius of curvature R2 is preferably at least twice the thickness t1 of the peripheral edge portion 19 of the bottom 18 and more preferably 2 to 5 times.

  The battery can 1 is inserted into the hollow portion of the die 32 from the bottom 18 side with its axis aligned with the axis of the die 32 with the electrode group and the electrolyte contained therein. Thereby, the connection part 22 of the battery can 1 and the contact part 38 of the die | dye 32 contact | abut in the contact start part P1, and the diameter reduction of the battery can 1 by the diameter reduction apparatus 30A (30B) is started.

Examples of the present invention will be described below. In addition, this invention is not limited to a following example.
Example 1
A battery can was formed by deep drawing a cold-rolled steel sheet having a thickness of 0.5 mm using a transfer press. And the groove | channel of width 1mm and depth 1mm was formed in the vicinity of the opening edge part of the side wall of a battery can so that a side wall might be made a round. Nickel plating was applied to the entire battery can. The battery can (side wall) had an initial outer diameter (diameter) D1 of 14.2 mm, and the bottom and side walls had a thickness of 0.3 mm. The radius of curvature R2 of the outer surface of the connecting portion between the bottom and the side wall was 0.7 mm. The outer diameter of the bottom before diameter reduction (the diameter of the circle drawn by the boundary X between the bottom and the connection portion) was 12.8 mm.

  An electrode group was configured by winding a laminate having a separator between a positive electrode and a negative electrode in a spiral shape. This was inserted into a battery can and an alkaline electrolyte was injected. Thereafter, a sealing plate also serving as a positive electrode terminal was attached to the opening end of the battery can with a gasket provided at the periphery, and the opening edge of the battery can was curled inward to seal the opening end. Ten test batteries were produced as described above.

  The battery cans of the ten test batteries were sequentially reduced in diameter using a diameter reducing device that reduced the diameter of the battery can with one die (32A) as shown in FIG. 2A. At this time, the cylindrical member was used for the part (henceforth a receiving type | mold) of the lower side support member 34 which contact | connects the bottom part of a battery can, The outer diameter was 13.5 mm. The inner diameter of the receiving mold was reduced by 4 mm. The center part of the bottom part was made not to contact the receiving mold. The inner diameter Dd of the contact portion of the die was 14 mm, and the radius of curvature R1 was 0.3 mm. The outer diameter Dc of the battery can after the reduction was 14 mm, which is the desired outer diameter D2, and the battery can was reduced by 0.2 mm. The contact start portion P1 was above the inner side surface SA1 (reference surface) in the axial direction of the battery can. Then, after the diameter reduction, the test battery was removed from the diameter reduction device, and the amount of deformation of the 10 test batteries with the bottom of the battery can bulging outward (downward) due to the diameter reduction was measured.

  A contact-type shape measuring device was used to measure the deformation. More specifically, the contact terminal (25 μm needle) of the measuring instrument is brought into contact with the outer surface of the bottom portion of the battery can and moved from the center of the bottom portion to the peripheral portion at a feed rate of 0.5 mm / second. The bottom shape before diameter reduction and after diameter reduction was obtained. Then, the bottom shape before the diameter reduction and the bottom shape after the diameter reduction were overlapped, and the deformation amount was measured by the maximum difference in shape (usually the displacement amount at the bottom center). Then, an average value of the deformation amounts of the ten test batteries was calculated to obtain a bottom bulge amount.

(Example 2)
The first die (32B) having an inner diameter of 14.1 mm and the second die (32C) same as the die (32A) of Example 1 having an inner diameter of 14 mm were used. After insertion into one die (32B), the diameter was reduced in the order of insertion into the second die (32C). Other than that was carried out similarly to Example 1, and reduced the diameter of ten test batteries, and obtained the bottom swelling amount. The radius of curvature of the contact portion of the first die (32B) is the same as the radius of curvature R1 of the contact portion of the second die (32C).

(Comparative Example 1)
As shown in FIG. 4, the test battery in which the initial outer diameter D1 of the side wall 20A of the battery can is 14.5 mm and the outer diameter of the bottom 18A before the diameter reduction is 13.1 mm is used. Ten test batteries were reduced in diameter in the same manner as in Example 1 except that the starting portion P1 was below the inner surface SA1 of the peripheral edge of the bottom in the axial direction of the battery can. The bottom bulge amount was obtained.

(Comparative Example 2)
As shown in FIG. 5, the radius of curvature (R2) of the connecting portion 22B is 0.4 mm, and the contact start portion P1 is lower than the inner side surface SA1 of the peripheral portion of the bottom in the axial direction of the battery can. 10 test batteries were reduced in diameter in the same manner as in Example 1 except that they were on the side, and the bottom bulge amount was obtained.

(Comparative Example 3)
As shown in FIG. 6, a battery can in which the connecting portion 22C has a nonuniform curvature radius, the connecting portion 22C and the side wall 20C are not tangent, and the can wall is bent at the boundary is used. The radius of curvature (R2) of the portion where the curvature of the connecting portion 22C is uniform was 1.2 mm. Further, the contact start portion P1 was lower than the inner side surface SA1 of the peripheral portion of the bottom in the axial direction of the battery can. Except for the above, the test batteries were reduced in diameter in the same manner as in Example 1 to obtain the bottom bulge amount. In Comparative Example 3, the center of the connection portion was at a horizontal distance of 0.7 mm from the outer surface of the side wall. When the side wall and the bottom are tangent, the distance is 1.2 mm. Therefore, in the comparative example 3, the center of the connecting portion is located closer to the side wall by 0.5 mm in the horizontal distance than when the side wall and the bottom are tangent. Such Comparative Example 3 corresponds to the fact that when the battery can is manufactured by deep drawing, the center of the connecting portion may be biased to the side wall depending on the deep drawing method and the mold to be used. To do.

  The above results are shown in Tables 1 and 2.

  As shown in Tables 1 and 2, Examples 1 and 2 had a bottom bulge amount of 0.04 mm or less, and almost no swelling of the bottom surface of the battery can was visually confirmed. On the other hand, in Comparative Examples 1 to 3, the bottom bulge amount was 0.22 mm or more, and the swelling of the bottom surface of the battery can was confirmed visually. In Comparative Examples 1 to 3, since the contact start portion P1 is lower than the inner side surface SA1 of the peripheral portion of the bottom in the axial direction of the battery can, the diameter reduction force F1 is reduced at the start of the diameter reduction. It is considered that the component force F2 in the radial direction of the battery can is deformed so as to bend the bottom. Further, since the diameter reducing force F1 itself is larger in Comparative Examples 1 to 3 than in Examples 1 and 2, the component force F3 in the axial direction of the battery can of the diameter reducing force F1 is also compared with that in Examples 1 and 2. It is thought that it has grown. As a result, it is considered that the amount of bottom bulge is increased because a rotational force (counterclockwise rotational force in FIG. 3 and the like) that tilts the side wall of the battery can inwardly acts on the can wall.

  By plotting, the inclination θ1 (angle between F3 and F1) of the diameter reduction force F1 from the axial direction of the battery can was obtained. In Examples 1 and 2, θ1 was 50 ° or more. On the other hand, in Comparative Examples 1 to 3, θ1 was 40 ° or less. As a result, in Examples 1 and 2, the component force F3 is smaller than the component force F2. Therefore, it is considered that the bottom of the battery can was prevented from swelling because the can wall of the battery can does not rotate counterclockwise in FIG. It is considered that θ1 is more preferably 60 ° or more.

  In addition, Example 2 in which a battery can was reduced in diameter by 0.1 mm step by step using two dies is an example in which only one die was used and 0.2 mm was reduced in diameter by one processing. The bottom bulge amount was smaller than 1. This is because, when a plurality of dies are used and the diameter is reduced in stages, the external force received by the battery can from one die is reduced, so that the bottom of the battery can can be prevented more effectively. It is thought that it was made. However, no difference was observed between the two by visual inspection. As described above, when the cylindrical battery is reduced in diameter by setting the contact start portion P1 above the inner surface SA1 of the peripheral edge of the bottom in the axial direction of the battery can, the bottom of the battery can is outside. It was confirmed that a battery having a good appearance shape was obtained without being deformed so as to swell.

  In Comparative Example 1, the outer diameter (diameter) of the battery can before diameter reduction is 14.5 mm, which is larger than Example 1 and the like, so that the space near the bottom of the battery can is widened, and the electrode group can be easily used as a battery can Could be inserted into. In particular, in the electrode on the outermost periphery of the electrode group, if the space near the bottom of the battery can is not wide, the electrode is bent, and as a result, the capacity is reduced due to short-circuit failure or dropping of the active material. Such an inconvenience could be avoided by setting the outer diameter of the battery can to 14.5 mm. In addition, when the electrolytic solution was poured into the battery can, the gap between the electrode group and the battery can was large, so that the electrolytic solution could easily penetrate into the electrode group. Moreover, it was possible to easily prevent the electrolyte from leaking out of the battery can. In Comparative Example 2, the space near the bottom of the battery can could be expanded by reducing the radius of curvature R2 of the connecting portion, so that the electrode group could be easily inserted into the battery can.

  According to the present invention, by satisfying at least the condition that the contact start portion is at a position on the opening end side of the battery can in the axial direction of the battery can relative to the inner surface of the peripheral edge of the bottom of the battery can, The deformation of the bottom of the battery can when the diameter of the battery can is reduced can be suppressed. Thereby, a cylindrical battery having a desired shape and size can be stably manufactured. When a plurality of dies having different inner diameters are used to reduce the diameter of the battery can in stages, it is only necessary that the above conditions be satisfied when each die actually contacts the battery can.

  While this invention has been described in terms of the presently preferred embodiments, such disclosure should not be construed as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains after reading the above disclosure. Accordingly, the appended claims should be construed to include all variations and modifications without departing from the true spirit and scope of this invention.

  DESCRIPTION OF SYMBOLS 1 ... Battery can, 2 ... Gasket, 3 ... Sealing plate, 4 ... Groove part, 6 ... Exterior label, 8 ... Hole, 9 ... Valve body, 10 ... Positive electrode terminal plate, 100 ... Battery, 10a ... Projection, 11 ... Electrode group , 12 ... Positive electrode, 13 ... Negative electrode, 14 ... Separator, 15 ... Positive electrode lead, 16 ... Insulating member, 17 ... Insulating member, 18, 18A, 18B, 18C ... Bottom, 19 ... Peripheral part, 20, 20A, 20B, 20C ... Side wall, 20a ... Open end, 22, 22A, 22B, 22C ... Connection part, 30A, 30B ... Diameter reducing device, 31 ... Moving mechanism, 32, 32A, 32B, 32C ... Dies, 33 ... Air cylinder, 35 ... Electric motor, 38: contact portion, R1, R2: curvature radius, D1: initial outer diameter, P1: contact start portion, SA1: inner surface, F1: reduced diameter force, F2, F3: component force

Claims (3)

A method of manufacturing a cylindrical battery comprising an electrode group including a positive electrode, a negative electrode, and a separator, and a battery can containing the electrode group,
The battery can includes a circular bottom, a cylindrical side wall having an open end, and a connection between the bottom and the side wall,
A step (a) of reducing the outer diameter Dc of the side wall from the initial outer diameter D1 after inserting the electrode group into the battery can;
The step (a) includes the step (a1) of inserting the battery can from the bottom side into a ring-shaped die having an inner diameter Dd smaller than the initial outer diameter D1, and the die at the opening end. Including a step (a2) of applying a diameter-reducing force to the battery can by relatively moving in the direction of
When the die and the battery can come into contact with each other and the application of the diameter reducing force is started, the contact start portion of the battery can is more than the inner surface of the peripheral edge of the bottom portion in the connection portion. position near the axial direction of the opening end portion side of the is,
Wherein the connecting portion of the battery can be subjected to step (a), that has only one bent portion having the battery the outside surface of the can battery can curvature radius R2 along the axial direction of the cylinder Type battery manufacturing method.   The method for manufacturing a cylindrical battery according to claim 1, wherein the outer diameter Dc of the side wall is reduced in a stepwise manner using a plurality of dies having different inner diameters Dd. The method for manufacturing a cylindrical battery according to claim 1 or 2, wherein the curvature radius R2 is 2 to 5 times the thickness of the peripheral edge of the bottom.

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